Methods of fabricating surface enhanced raman scattering substrates

Abstract

A method of fabricating a surface enhanced Raman scattering (SERS) substrate. In one embodiment, the method has the steps of simultaneously evaporating a metal at a first evaporation rate and a polymer at a second evaporation rate different from the first evaporation rate, to form a nanocomposite of the metal and the polymer, depositing the nanocomposite onto a substrate, and applying an etching process to the deposited nanocomposite on the substrate to remove the polymer material, thereby forming an SERS substrate.

1. A method of fabricating a surface enhanced Raman scattering (SERS) substrate, comprising the steps of:
 (a) simultaneously evaporating a metal at a first evaporation rate and a polymer at a second evaporation rate different from the first evaporation rate, to form a nanocomposite of the metal and the polymer; 
 (b) depositing the nanocomposite onto a substrate; and 
 (c) applying an etching process to the deposited nanocomposite on the substrate to remove the polymer material, thereby forming an SERS substrate comprising a network of nanoparticles of the metal, the nanoparticles having an average size ranging from about 10 nm to about 30 nm, and an inter-particle gap being less than about 1.5 nm. 
 
     
     
       2. The method of  claim 1 , wherein each nanoparticle has an fcc crystalline structure. 
     
     
       3. An SERS substrate formed according to the method of  claim 1 . 
     
     
       4. A method of fabricating a surface enhanced Raman spectroscopy (SERS) substrate, comprising the steps of:
 (a) simultaneously evaporating a first material at a first evaporation rate and a second material at a second evaporation rate that is different from the first evaporation rate to form a composite of the first material and the second material; 
 (b) depositing the composite onto a substrate; and 
 (c) removing the second material from the deposited composite on the substrate, thereby forming an SERS substrate comprising a network of nanoparticles of the first material, the nanoparticles having an average size ranging from about 10 nm to about 30 nm, and an inter-particle gap being less than about 1.5 nm. 
 
     
     
       5. The method of  claim 4 , wherein the first material is a metal and the second material is a polymer. 
     
     
       6. The method of  claim 5 , wherein the first material comprises at least one of silver and gold. 
     
     
       7. The method of  claim 5 , wherein the second material comprises Teflon AF®. 
     
     
       8. The method of  claim 4 , wherein each nanoparticle has an fcc crystalline structure. 
     
     
       9. The method of  claim 4 , wherein the step of simultaneously evaporating the first material and the second material to form the composite comprises the step of performing electron-beam assisted vapor-phase codeposition of the first material and the second material without causing decomposition of the second material. 
     
     
       10. The method of  claim 4 , wherein the step of removing the second material further comprises the steps of:
 (a) sputtering at least one film of the first material onto one side of the composite; and 
 (b) exposing the entire composite to a plasma etching treatment for a predetermined time for removing the matrix of the second material while retaining the structures of the first material. 
 
     
     
       11. The method of  claim 10 , wherein the predetermined time is about 2 minutes. 
     
     
       12. An SERS substrate formed according to the method of  claim 4 . 
     
     
       13. An SERS substrate formed according to the method of  claim 10 . 
     
     
       14. A method of identifying a chemical or biological sample, comprising the steps of:
 (a) fabricating a surface enhanced Raman spectroscopy (SERS) substrate, wherein the SERS substrate comprises a network of nanoparticles of a metal, the nanoparticles having an average size ranging from about 10 nm to about 30 nm, and an inter-particle gap being less than about 1.5 nm; 
 (b) placing a solution containing the chemical or biological sample on the SERS substrate; 
 (c) performing a Raman analysis on the sample; and 
 (d) comparing the Raman signal generated from the sample on the SERS substrate with a signal from a control solution so as to identify the sample. 
 
     
     
       15. The method of  claim 14 , wherein the metal in the fractal metal-polymer nanocomposite comprises silver or gold, and wherein the polymer in the fractal metal-polymer nanocomposite is Teflon AF®. 
     
     
       16. The method of  claim 14 , wherein the sample comprises double-stranded deoxyribonucleic acid. 
     
     
       17. A method of fabricating a surface enhanced Raman scattering (SERS) substrate, comprising the steps of: (a) simultaneously evaporating a metal at a first evaporation rate and a polymer at a second evaporation rate different from the first evaporation rate, to form a nanocomposite of the metal and the polymer; (b) providing a substrate that has a first side, and an opposite, second side; (c) depositing the nanocomposite onto the first side of the substrate; (d) sputtering a film of the metal onto the nanocomposite deposited on the first side of the substrate to form a layered structure with the film of the metal, as a first layer, formed on a layer of the nanocomposite, as a second layer; and (e) exposing the layered structure to a plasma etching with the second layer facing the plasma to remove the polymer material, thereby forming an SERS substrate, wherein as formed, the SERS substrate comprises a network of nanoparticles of the metal, the nanoparticles having an average size ranging from about 10 nm to about 30 nm, and an inter-particle gap being less than about 1.5 nm. 
     
     
       18. The method of  claim 17 , wherein the at least one metal comprises silver or gold, and wherein the at least one polymer comprises Teflon AF®.